Children are extremely susceptible to respiratory infections.

From the nose and throat, air travels down the neck into the windpipe (the trachea). As it enters into the chest area, the trachea divides into two main tubes, the right and left bronchi.

Each bronchus carries air to the right and left lung, respectively. As the bronchus enters the lung, it divides into smaller and smaller bronchi, much the same as large branches of a tree divide into smaller branches and finally twigs. These smallest...